Synthesis of camphor



.40 and many of which occur in dextro, laevoand 110 g. of hydrated lime and 5900 cc. of water are 40 .45 rosin of various varieties of pine and hence is precipitate washed free of calcium nitrate. It is 4 55 pounds andmus be liquid at the temperature of heatedto about 175 C. and the toluene allowed Patented Dec. 11, 1934 I 1 UNITED STATES PATENT OFFICE r 1,983, 2 SYNTHESIS or CAMI'HOR I K, I;I 3 erg er,' Wilmington, Del., assignor to E I. du- Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware Serial No. 498,204

12 Claims. (01. 260-133) No Drawing Application November 25, 193 0,

This invention relates to. aprocess for producreaction. The mass must also be alkaline. The ing camphor, synthetically, and more particularcatalyst must be in a finely divided condition. In ly-is: concerned With an improvement in processes order to make the mechanical operation simple for the manufacture of camphor from borneol. there should be present some solvent which 5 It is known that, isoborneol can be oxidized into boil and condense below the subliming point of i 5 camphorin the, presence of water and alkalies borneol or camphor so as to keep the apparatus by means o certain oxidizing agents such as perdome clear and to keep the borneol in the field of oxide, manganese and copper oxide (see U. S reaction. At the start solvent is also necessary Patent No. 9.89 ,65l, April 18, 1911) .7 Moreover, it to render the mass liquid at the reacting temperais known that hydrogen can be split off from many ture. The amount of solvent present, however, organic, compounds by heating them to high temshould be kept at a minimum as it tends to slow peratures in the presence of finely divided metals, up the reaction. Along with the alkaline. condisuch as finely divided copper, nickel, etc., the tion the. catalyst must function at temperatures metals being present in small amounts and acting below 200" G. to avoid dehydration. A slight reeatal ioally. hi pro es h been applied to action oc urs at temperatu s app ox m t n the catalytic dehydrogenation of borneol (see 125 C. Best results are, however, obtained at the U. S. Patent No, 994,437, June 6, 1911). Since preferred temperatures indicated in the examples. the yields are low, both of; these processes are un- It has been found that a highly reactive catalyst satisfactory forthe commercial production of suitable for use. in the process may be produced in camphor. Moreover, in the first mentioned situ together with the desired alkalinity and water 20 process, h co oi e materia re ui d is pr by means o t p e i e mpo tion unde hibitive while, the second process, the yields the influence of heat of a calcium hydroxide coporepa ti ul rl nsa sf ctory due t the dehype hydrox de complex, while t h s me time, dration of the borneol rather thanthe dehydroproviding the means for boiling off the excess of genat o The tempe atures ar also i onwater as f ed h p s ve compo ion 25 veniently high. of the complex maintains the desired alkalinity, Accordingly, it is the object of the present incatalyst and water, which of course is drawn off vention to devise a method for the production of substantially as fast as formed, present throughcamphor from borneol which is at once cornrnerout the course of the reaction. cially feasible and productive of high yields,- The following examples of specific embodi- 30 With these objects in view, I have found that ments are furnished as illustrations of a satis- ,camphor can be produced from borneol with high factory procedure to be followed in carrying out yields by dehydrogenating theborneol catalytithe process. Itwill be understood that the incally in the liquid phase in an alkaline reaction vention is. not limited to the specific proportions and in the presence of a catalyst. or conditions therein set forth. 35

By theterm borneol I do not refer in general Exam [6 I to that. class of compounds which includes borneol, isoborneol, camphene hydrate and methyl The complex for furnishing the water, alkali camphenilol all of which are chemical isomers and catalyst is first prepared. For this purpose dextro laevo forms, but I do refer specifically to put into an agitated vessel To this matter is the borneol which is produced in nature in many added during 2 hours, while thoroughly agitated, plant organisms; occurs as acetate in Siberian a solution of 24 g. of copper nitrate in 300 cc. of and Nordish pine oil; and is found in the stump Water. The resulting mass is filtered and the contained in American pine oil. It is also prothen dried at C, and gently reduced to such a duced from bornyl chloride by the Grignard size as to pass through a 30 mesh screen. Violent reaction. treatment should be avoided inasmuch as it In carrying out this process the borneol eminjures the reactivity. A vessel provided with 50 ployed should be pure and particularly should not an agitator and means to maintain it at about be contaminated with ethers or esters or with 180 C, is then charged with g. of borneol tertiary alcohols of the terpene series. which has been previously purified and with I Thereacticn mass should contain no catalytic 25 cc. of toluene and 2 cc. of higheboiling solvent poison such as chlorine compounds or sulfur comnaphtha (B. P. 170 C.). This mixture is to distill off. By this step the last trace of free 'water is removed. Approximately 10 g. of the previously prepared catalyst-forming material described above is thereupon added. The mixture is continuously agitated and" held at 175-185 C. while the hydrogen and the water formed escape along with a little of the solvent naphtha. The mass in the Vessel is then dissolved. in alcohol and filtered. The camphor may be recovered from the reaction mixture in any well known way, for example, by crystallization or by sublimation. A yield of about g. is

obtained. W

Example II On a large scale, less than half the proportionate amount of catalyst employed in Example I is necessary and the catalyst-forming material instead of being added all at once is added gradually the rate of addition being controlled by the violence of the reaction; For instance, about 3400 lbs; of borneol are charged into a 600 gal. kettle provided with an agitator and a heating device where it is mixed with about 340 lbs. of fresh commercial coal tar naphtha. When heat is applied the whole mass is dried by the simultaneous evolution of the vapors of coal tar naphtha and water. While some coal tar naphtha is still left in the mass and with the temperature at about 175 0., about 2 lbs. of the catalyst-forming material is added and then successively 1 lb. at a time isadded as the violence of the reaction permits, while the temperature is maintained at between about 175 and 180 C. When about lbs. of the catalyst-forming material have been added, during a period' of about 50 hours, the reaction is complete. It is important that there be some coal tar naphtha remaining to the end of the reaction. The camphor may be recovered from the reaction mixture in any well known way, for example, by crystallization or by sublimation.

It will be obvious to any chemist skilled in the art that other catalyst-forming materials may be employed than that specifically disclosed hereinabove. The essential condition for such materials is that they be capable when added to the reaction mixture of furnishing in situ the alkali and water in addition to a dehydrogenating catalyst. Obviously, other solvents than naphtha may be employed and the temperature may be varied, although as already statedi the temperatures disclosed in the examples represent the preferred range. Obviously; also if desired the catalyst, alkali and water can be added separately, it being understood that under these circumstances the water would be removed practically as fast as added.

below the subliming point of borneol and less than about 10%, based on the weight of borneol, of a calcium hydroxide-copper hydroxide complex adapted under the conditions of the reaction to form a dehydrogenating catalyst, water ,and alkali.

2.'The process of producing camphor which comprises heating borneol to a temperature between and 200 C. in the presence of a solvent boiling at a temperature below the subliming point of borneol and less than about 10%, based on the weight of borneol, of a calcium hydroxide-copper hydroxide complex prepared by reacting calcium hydroxide with copper nitrate. I Y

3. The process of producing camphor which comprises heating borneol to a temperature between 125 and 200 C. in the presence of naphtha and less than about 10%, based on the weight of borneol, of a calcium hydroxide-copper hydroxide complex prepared by reacting about 110 parts by weight of calcium hydroxide with 24 parts by weight of copper nitrate in water solution and filtering to obtain theprecipitate.

4. The process of producing camphor from borneol which comprises mixing about 340 parts by weight of borneol with 34 parts of naphtha, heating to about 0., adding in successive stages, while maintaining the temperature between 175 and 180 0., about 1 6- part of a calcium hydroxide-copper hydroxide complex (adapted upon heating to'yield alkali, water and a dehydrogenating catalyst) until about 12 parts have been added and thereafter removing the camphor. e r

5. The process of producing camphor which comprises heating borneol to a temperature between 125 C. and 200 C. in the presence of less than about 10%, based on the weight of borneol, of a calcium hydroxide-copper hydroxide catalyst.

6. In a process of producing camphor which comprises heating borneol to a temperature between 125 C. and 200 C. in the presence of a solvent adapted to condense at a temperature belowthe subliming point of borneol under the conditions of reaction and in the presence of a calcium hydroxide-copper hydroxide catalyst, the step which comprises adding to the reaction zone during the course of the reaction a calcium hydroxide-copperhydroxide catalyst in such proportions thatthe total amount of catalyst does not exceed about 10% by weight of borneol present in the reaction zone.

7; The process of producing camphor which comprises heating borneol to a temperature between about 175 C. and about C. in the presence of naphtha and less than about 10%, based on the weight of borneol, of a calcium hydroxide-copper hydroxide catalyst.

8. The process of producing camphor which comprises heating borneol to a temperature between 125 C. and 200 C. in the presence of a solvent adapted to condense at a temperature below the subliming point of borneol and less than about 10%; based on the weight of borneol, of acalcium hydroxide-copper hydroxide complex prepared by agitating calcium hydroxide and copper nitrate in water solution, isolating the solid product and gently reducing it to relatively small size particles.

9. The process of producing camphor which comprises subjecting borneol to dehydrogenation in the presence of water, the amount of water being not substantially greater than that formed when the same amount of borneol is heated at a temperature of about 175 C. in the presence of about 10%, based on the weight of borneol, of acalcium hydroxide-copper hydroxide catalyst prepared by reacting about 110 parts by weight of calcium hydoxide with about 24 parts by-weight of copper nitrate'in water 50111- tion, filtering and drying the residue at about 60 C.

10. The process of producing camphor which comprises subjecting borneol to dehydrogenation by heating in the presence of alkali, a dehydrogenation catalyst and Water, the amount of water being not substantially greater than that formed when the same amount of borneol is heated to a temperature of about 175 C. in the presence of about 10%, based on the weight of borneol, of a calcium hydroxide-copper hydroxide catalyst prepared by reacting about 110 parts by weight of calcium hydroxide With about 24 parts by weight of copper nitrate in water solution, filtering and drying the residue at about 60 C.

11. The process of claim 10, in which a solvent is present during the dehydrogenation.

12. The process of claim 10, in which the water is formed in situ in the reaction mixture and is removed as the reaction proceeds.

ERNST K. H. BERGER. 

